Sunday, November 23, 2014

The CMOS sensor of ASI 120mm is quite sensitive in creating Newton's ring. I found it's pretty terrible in the last imaging session. People suggested that Newton's ring could be removed by tilting but then it involves on more adapter and it's not really a good way indeed.

An alternative approach is to do a flat field which can remove the Newton's ring as well as any dust on the CCD. A flat field could be acquired by de-focusing the image a large bit, and I found it natural for the whole work flow. I normally do a prime focus shot, and then pump up the magnification by adding a barlows/powermate, and before I refocus with the barlows/powermate, I simply capture a flat field first!

First up is a mosaic of two shots, taken at 1151 and 1153 (GMT+8) respectively.

So, two shots were taken afterward by using the method above with a flat field. The first one is done very close to the flat field, so the Newton's rings were removed completely. It's taken at 1157 (GMT+8):-

Next one is taken at 1159 (GMT+8), I don't exactly know, but seems like the Newton's ring is not as cleanly removed as above.

There might be two reasons:

1. field rotation since I'm doing alt-az tracking with the Nexstar SE mount, I found it unlikely, however

2. the flat field was not done correctly, since the solar disc was not occupying the whole frame, so the flat field is only partial, some dark corner was not illuminated afterall

So, next time when I do a flat field, I shall move the camera to the center of the solar disc.

Friday, November 21, 2014

Formerly, this room was my playing room. There is only a computer, and a store room of my equipments. But then when my daughters have to learn piano, I need to spare some rooms and so I sold my C8 and downsized to a C5.

Recently, my daughters requested their own room, so I have to move out from this playing room altogether. My faithful self-design computer desk with storage cabinet has to be thrown away. Actually, the upper half had been discarded when the piano moved in but now the whole thing would be gone soon.

I'll need to find a replacement. Last night, I've measured the window platform of my own room and I found that it was 42" (width) x 22" (depth) and then I could make a cabinet as high as 16" without blocking the windows. This cabinet will be tailor made to store all my existing stuff inside, and I will be taking photographs from inside by using my Nexstar SE mount there and there should be enough room. However, I couldn't use my desktop PC to take images by then and I've to go back to my Eee PC which should suffer from much lower frame rate? Maybe it's time to upgrade with a better computer?

Before it was killed, let's take a photographs in remembrance:

Top most level for my Camera gear which consists of a Canon 450D, a kit lens, a 50mm f1.8, a 8mm fisheye and a Canon 200mm f2.8L plus a Kenko 2x, a couple of manual macro tubes, shutter release, flash, etc. And there are two new members namely the ASI 130mm and ASI 130mc.

On the second level is my trusted Ranger, my Mark-X, eyepieces and accessories box.

On the third slim level is my Canon 10x30 IS, and some miscellaneous stuff.

Thursday, November 13, 2014

The answer is two of them! I got myself an ASI 120MM and an ASI 120MC, the monochromatic model is for solar and lunar imaging, while the color one is for planets. Frankly, with only a C5 as my biggest telescope, I believe that I will let the color one go soon. But anyway, why not give a trial? I had success with a DBK and a C5, so I'm pretty confident that the ASI will do the job nicely as well.

The general impression is excellent.

Packaging is simple but works. It comes with a lens, a 1.25" nosepiece, a driver CD, a very nice USB cable, and you even get a ST4 cable!

Installation is SUPER EASY as mentioned in the user guide.

The software is easy to use, too.

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The software and the driver are rather stable, but this is only my first impression. Sharpcap is easy to use and pretty powerful.

I've to update my Registax 5 to the latest release to support the Mono8 codec, RGB24 is fine as expected, no need to upgrade.

These were pretty dark, I have to use very high gain and relatively long exposure (~1s) to get images like the above. Not bad, I would say. Not a huge improvement over my Lumenera nor DMK, but I should test again with astronomical targets.

These two cameras were again close to par-focal with my Japanese Widescan 20mm Type III, nice plus.